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Editors' Choice

Top-down or bottom-up?

Was climate warming more important than megafaunal loss for shaping postglacial landscapes in Britain?

ILLUSTRATION: ALICE TURNER/STOCKTREK IMAGES/SCIENCE SOURCE

Primary producers and animal consumers interact to determine the structure and function of ecosystems, but how do their relative influences change over time? Jeffers et al. used the fossil record of the late Quaternary in Britain and Ireland to study whether the extinction of two-thirds of the native megaherbivores (including mammoths, giant deer, moose, and others) led to the observed expansion of woody plants at the end of the last glacial period. Instead, they found that more influential factors were a warming climate and reduction in fire, with an even more pronounced role for increasing shrub encroachment (followed by trees) in determining ecosystem structure. Plants and plant-soil feedbacks may have been more important than trophic interactions in driving the changes as northern ecosystems moved into the postglacial period.

Ecol. Lett. 10.1111/ele.12944 (2018).

Molecular Biology

Stress granule transcription

Steve Mao

When translation initiation is stalled under stress, nontranslating messenger ribonucleoproteins form insoluble assemblies called stress granules (SGs) in the cytosol. Namkoong et al. sequenced all transcripts from purified SGs. They found that although translation of most transcripts is inhibited, only a subset of transcripts form SGs. The length and abundance of the AU-rich elements are key features determining SG-targeting specificity, agreeing with a recent report by Van Treeck et al. showing that RNA self-assembly drives SG formation. SGs have been implicated in cancer and neurodegenerative diseases; understanding the specificity of their RNA components and the principles of their formation offers insights into their pathological contribution.

Stop the clock: Tenure, gender, and children

Brad Wible

Allowing both male and female faculty to stop their tenure clock when having a child can increase tenure rates for the former and reduce them for the latter. Antecol et al. analyzed data on all assistant-professor hires at top-50 economics departments from 1980 to 2005; 44% of women and 47% of men had a child within 5 years of completing their Ph.D., before typical tenure deadlines. Differential effects of clock policies on tenure are driven by the fact that men publish more in top-tier journals after policies take effect, whereas women do not. Policies may not compensate for the specific productivity challenges that women face after childbirth. Despite this early setback, and the subsequent career churn, clock policies do not hurt women's chances of ultimately gaining tenure in the profession.

Amer. Econ. Rev. 10.1257/aer.20160613 (2018).

Chemistry

Early warning about emerging contaminants

Julia Fahrenkamp-Uppenbrink

Contamination of environmental samples with harmful chemicals can be detected with high-resolution mass spectrometry (HRMS). This method can provide accurate mass data for the complex mixtures, thus allowing retrospective analysis to look for newly identified contaminants. Alygizakis et al. report on a pilot study involving eight reference laboratories in Europe and Australia to investigate whether retrospective screening of HRMS data can be used to establish the extent of a newly identified contaminant's presence in the environment. On the basis of archived data from 48 diverse environmental samples from 14 countries, the study documents widespread occurrence of several chemicals not commonly included in monitoring of environmental samples. Expanding the pilot to a full early-warning system for global emerging contaminants will require a virtual data repository with agreed-upon data standards.

Environ. Sci. Technol. 10.1021/acs.est.8b00365 (2018).

Vascular Biology

Sensing the stress

Lisa D. Chong

When blood flow in arteries increases, surrounding smooth muscle relaxes to allow blood vessel dilation. Using a high-throughput screen for mechanoreceptors that are sensitive to blood flow (shear stress), Xu et al. identified a type of sensor expressed by vascular endothelial cells called G protein–coupled receptor 68 (GPR68). Its activation triggers a cell signaling pathway that increases intracellular calcium concentration, an event that is associated with vasodilation. The authors discovered that GPR68 is expressed in mammalian small-diameter blood vessels and that loss of GPR68 expression in mice disrupts the vasodilatory response to increased blood flow. Moreover, a compound that activates GPR68 activity increased vasodilation, indicating that drugs targeting this stress sensor could potentially treat cardiovascular disease.

Cell173, 762 (2018).

Structural Biology

Dynamic fibrils drive protein assembly

Valda Vinson

A low-complexity domain of the protein FUS plays a role in forming RNA granules. Luo et al. identify and structurally characterize two reversible amyloid cores (RACs) in this domain. In stable amyloid fibrils, β-strands stack to form β-sheets that pack tightly and exclude water. In contrast, RAC1 forms a kinked coil that stacks along the fibril axis; two such layers interact through tyrosine ring stacking. RAC2 forms β-sheets, but with water molecules between mating sheets. It is already established that the LARK (low-complexity amyloid-like kinked segment) may be broadly involved in membraneless assemblies. The RAC2 structure suggests that reversible fibril formation may occur without kinking.

Nat. Struct. Mol. Biol.25, 341 (2018).

Cooling Textiles

Scaling up textiles that cool down

Brent Grocholski

Decreasing energy consumption by reducing the need for air conditioning helps combat CO2 emissions and promotes sustainability. Peng et al. present a remarkable scale-up of nanoporous polyethylene microfibers for use in cooling fabrics. These fabrics allow heat to radiate through them while reflecting visible light and can be engineered for wearability. The ability to scale up production is important for making this material cost-effective relative to cotton and other mass-produced textiles. Incorporating cooling fabrics into everyday wardrobes presents an opportunity to decrease indoor cooling.